1. Field of the Invention
This invention relates to materials technology and more particularly to protective coatings. In one of its more particular aspects the present invention is directed to multipurpose coatings having properties which make them useful for protecting surfaces exposed to fire, thermal fluxes, corrosion, destructive chemical agents, such as acids, alkalies and other strong electrolytes, and microorganisms.
2. Description of Related Art
Various surfaces have been protected against combustion by means of coatings containing fireproofing compounds as fillers. A disadvantage of the use of such fireproofing materials is that it has not been possible to achieve comprehensive multi-function heat protection at heat levels exceeding about 120 J/m.sup.2. Nor do such materials protect against damage from open flames, acids, alkalies, and other corrosive liquids or microbiological agents.
A fire-resistant protective coating composition for wood products is disclosed in Inventor's Certificate, USSR 2822988/23-26, 1979. The composition contains 8.0-11.7 parts by mass dolomite sand, 8.0-10 parts expanded perlite, 1.2-2.6 parts asbestos fiber, 42-53.6 parts aluminochromium phosphate binder, 19.5-32.9 parts urea formaldehyde resin, and water. The composition is applied to wood by means of a brush or sprayer, dried for 2-3 hours, and hardened for 24 hours.
In evaluating the fire-resistant properties of the coating it was found that mass losses equaled 2.5-3.3% with zero combustion. The disadvantages of this coating include its poor adhesion, especially to metallic surfaces, its tendency to promote corrosion under humid conditions, and its support of microorganism and algae growth.
A composition and method for obtaining a heat-resistant protective coating for titanium and associated alloy products is disclosed in Inventor's Certificate, USSR 1654339 23-5, 1971. An aqueous colloidal graphite composition is applied to a titanium surface. The composition contains the following components, in percent by weight:
______________________________________ colloidal graphite 30-70 colloidal fire clay 0.1-5 magnesium oxide 0.1-1 ammonia solution (25% solution) 1-5 surfactant 0.1-1 water 24-63 ______________________________________
This heat-resistant coating provides oxidation protection to titanium and its alloys when heated to temperatures of 1050.degree. C. in air. The coating has good lubricant and adhesive properties as well as good wettability. The strong plastic properties of the coating permit repeated heating of the coated surfaces and hot deformation without repainting.
The colloidal fire clay is prepared by mixing 15% fire clay with 1% magnesium oxide, and then stirring in water. Water-soluble oxyethylated alkylphenol surfactants are added to the required water quantity, after which a 25% ammonia solution, colloidal fire clay, and colloidal graphite are added. The coating is applied by immersion to a metal surface preheated to a temperature of 100.degree. C. The coated surface is then dried in a drying oven at a temperature of 110.degree.-120.degree. C. until completely dry.
Some of the drawbacks of this method of producing a fire-resistant coating are the lack of multi-function protective capabilities, water sensitivity of the coated surface, sensitivity to corrosion, sensitivity to microorganisms and algae, and poor mechanical strength.
It is accordingly an object of the present invention to increase the heat resistance of coatings for metals and other substrates.
Another object is to expand the field of application and the protective functions of the coatings.
Another object of this invention is to increase the resistance of coated surfaces to open flame, strong heat fluxes, and radiation, as well as chemical agents, microorganisms, and weather factors.